Correlation of electric field and critical design parameters for ferroelectric tunable microwave filters

The correlation of electric field and critical design parameters such as th e insertion loss, frequency tunability, return loss, and bandwidth of condu ctor/ferroelectric/dielectric microstrip tunable K-band microwave filters i s discussed in this work. This work is based primarily on barium strontium titanate (BSTO) ferroelectric thin film based tunable microstrip filters fo r room temperature applications. Two new parameters which we believe will s implify the evaluation of ferroelectric thin films for tunable microwave fi lters, are defined. The first of these, called the sensitivity parameter, i s defined as the incremental change in center frequency with incremental ch ange in maximum applied electric field (E (PEAK)) in the filter. The other, the loss parameter, is defined as the incremental or decremental change in insertion loss of the filter with incremental change in maximum applied el ectric field. At room temperature, the Au/BSTO/LAO microstrip filters exhib ited a sensitivity parameter value between 15 and 5 MHz/cm/kV. The loss par ameter varied for different bias configurations used for electrically tunin g the filter. The loss parameter varied from 0.05 to 0.01 dB/cm/kV at room temperature.